Influence of dynamic factors on ice rafting
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Influence of dynamic factors on ice rafting LI Chunhua1∗ , SUN Hequan2 1 2
National Marine Environmental Forecasting Center, Beijing 100081, China Dalian Naval Academy, Dalian 116018, China
Received 15 May 2009; accepted 9 February 2010 ©The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg 2010
Abstract Theoretical analysis and numerical simulation have been applied to researching the effect of wave, current and wind on the ice rafting. The analytical results show that wave is the key factor for ice fracture. The process of ice rafting is simulated using the discrete element method. The simulated results show that the distortion or flexure breakage happens firstly, then followed by ice rafting. The comprehensively analysed results show that the ice is easily rafted on the simultaneity action of wave, current and wind, and the action of wave can’t be ignored. Moreover, the rafted ice length increases with the enhancive force of ocean current and wind. Key words: sea ice, rafted ice, Bohai Sea
1 Introduction Rafted ice is ubiquitous in the Bohai Sea. It can prominently affect navigation and platform production for its rather great thickness. The study of rafted ice forming characters is important to analyze the reliability of ice design parameters on offshore structures. The research on ice rafting is not enough although the disciplinarian of level ice thickness variety has been mastered in the Bohai Sea. A great deal of investigations and basic studies need to be made in order to obtain the mechanism of ice rafting. The initial research about ice rafting was on the Arctic ice. It appears commonly in the early freezing days and in the seasonal ice covered ocean. The determination of rafting ice thickness is a research hotspot in the previous study. Parmerter (1975) found that the largest ice thickness is 0.17 m to raft with his model calculation. At the same time, he pointed out that thicker ice rafting might happen due to the varied ice intensity in the different sea areas. Kovacs (1974) observed the rafted ice with 3.3 m thickness in the Beaufort Sea. Babko (2002) obtained that the ice rafting played an important role in the ice thickness distribution in the Arctic. Hopkins (1999, 2004) analyzed the critical condition with numerical simulations and physical experimentations. Marchenko (2005) elaborated dynamic models of ice rafting and ice ridge build-up. All the researches above can be
referred to study the ice rafting in the Bohai Sea. Some investigations on rafted ice in the Bohai Sea have been carried out. There are two types of rafted ice in the Bohai Sea (Li, 1997). One is the finger rafted ice that mainly exists in the early freezing area covered with the thin ice and the intension is infirm, as shown in Fig. 1. The other is the layer rafted ice as in Fig. 2, which is formed in the area covered with
Fig.1. Finger ice rafting.
Fig.2. Multilayer ice rafting.
Foundation item: The National Natural Science Foundation of China under contract Nos 40506009 and 908-02-03’ National Project. author
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